Development and Validation of Analytical HPLC-UV Method for simultaneous estimation of Losartan and its active Metabolite EXP-3174

Abstract

Background: The combination therapy of Losartan and active metabolite has proven to be beneficial as compare to either drug monotherapy. Losartan is a highly selective, orally active, non-peptide angiotensin II receptor antagonist indicated for the treatment of hypertension, which is one of the most important causes of mortality and morbidity in the modern world. It has a more potent active carboxylic acid metabolite EXP-3174 (2-butyl-5-chloro-3-[[4-[2-(2H-tetrazol yl)phenyl]phenyl]methyl]imidazole-4-carboxylic acid). Losartan and its active carboxylic acid metabolite EXP-3174 block the vasoconstrictor and aldosterone-secreting effects of angiotensin II by type ATI receptor blockage. Following oral administration, losartan is rapidly absorbed, reaching maximum concentrations 1–2 h post-dose. Result: The selected analytes were effectively separated on thermo β-basic C18 (100×4.6 mm, 5 µm) column using mobile phase consisting of 20mM monobasic potassium phosphate and 0.2% TEA with acetonitrile and iso-propyl alcohol in gradient mode. The eluent was monitored at 228nm at 1.0 ml min-1 flow rate. The total run time was less than 12 min. Conclusion: The active carboxylic acid metabolite E-3174 is about ten times more potent than losartan. In healthy volunteers, the concentrations of the active carboxylic acid metabolite EXP-3174 were found to be more closely parallel angiotensin II antagonism than those of the parent compound. Thus, the angiotensin II blocking activity of losartan is predominantly based on its major active carboxylic acid metabolite EXP-3174. Given this as background and to our best knowledge, there is no HPLC-UV method available or published simultaneous estimation of losartan with its active metabolite.